1. FIELD OF THE INVENTION
The present invention relates to an improved process for producing 3-anilino-5-pyrazolones.
2. DESCRIPTION OF THE PRIOR ART
3-Anilino-5-pyrazolones are useful compounds as intermediates for dyestuffs or as magenta color formers. Of the 3-anilino-5-pyrazolones, compounds having a substituent such as a halogen atom, an alkyl group or an alkoxy group in the 2-position of the 3-anilino group and a hydrophobic group containing 6 or more carbon atoms in the 3-anilino group are very useful as magenta color formers, because they have particularly excellent photographic properties.
Hitherto, many processes have been suggested in order to synthesize the 3-anilino-5-pyrazolones. However, these processes have the defects that either the process is complicated, the reaction yield is low or the starting materials are expensive, etc. Of these processes, the process described in British Pat. 1,129,333, namely, the process which comprises reacting .beta.-anilino-.beta.-alkoxyacrylates with hydrazines in the presence of an alkali metal alkoxide, is most effective. However, the yield of this process is not always high. Particularly, when this process is applied to the synthesis of pyrazolones having a hydrophobic group in the 3-anilino group, the desired 3-anilino-5-pyrazolones are hardly obtained or obtained in a very small amount.